Relay



Oct. 2, 1945. J JOHNSTON 2,385,994

RELAY Filed Nov. 26, 1945 Patented Oct. 2, 1945 RELAY Arthur J.Johnston, Park Ridge, Ill., assignor to C. P. Clare & 00., Chicago,111., a corporation oi Illinois Application November 26, 1943, SerialNo. 511,815

9 Claims.

The present invention relates in general to relays, and the object ofthe invention is to produce a new and improved relay.

More in particular, the invention relates to relays oi the type in whichso-called contact springs are employed to open or close electricalcircuits. A well known relay of this type is commonly referred to as atelephone relay. Such relays may have one or more working contactsprings, or armature springs, and so-called make contact springs orbreak contact springs with which the working contact springs cooperate.They find application not only in telephone systems but in various typesof selection and control systems.

A defect in telephone relays and other relays in which make or breakcontact springs are empioyed is what is generally known as contactbounce. To explain what is meant by this term a simple relay having anarmature spring and a cooperating make contact spring may be referredto. When the relay is energized the armature is sharply attracted andthe working contact spring is moved suddenly into engagement with themake contact spring, striking the latter a sharp blow, which tends tomake it vibrate. The vibrations, when they occur, are of relatively highfrequency and are highly damped. The extent-to which the vibrationsoccur depends on the adjustment of the relay and various other factorswhich need not be gone into. The effect of the vibrations depends ontheir amplitude, which may be enough to open the circuit, perhaps two orthree times, beiore the vibrations die out and the contact becomessolidly closed.

Contact bounce can be detected by means of a cathode ray oscillograph,having a suitable sweep voltage applied to the horizontal deflectorplates and using the relay contacts to be tested to apply a directcurrent voltage to the vertical deflector plates. If no contact bouncetakes place the ray will be deflected when the relay is energized andthe deflection will be maintained until the relay is deenergized;whereas if contact bounce is present the initial deflection of the mywill not be maintained but the ray will make one or more rapidincursions toward the normal line. These rapid inmrruptions in thedeflection are caused by high frequency vibrations of the make contactspring which open the circuit.

Contact bounce may also take place at a break contact spring when therelay is denergized and the working contact spring comes into engagementwith the break contact spring.

Contact bounce does no particular harm under many circuit conditions. Inthe case of a relay which simply closes a low current circuit and holdsit closed for a few seconds or longer, contact bounce is usually of noappreciable effect and is more or less unobjectionabie. If the samerelay is used to start a direct current motor, however, and if contactbounce is present, the motor circuit will be opened at a time when themotor is taking a heavy current and destructive arcing will occur.Another illustration is an impulsing relay, controlled over a linecircuit and delivering impulses to the motor magnet of a steppingmechanism. If the impulsing relay operates at a slow speed, thearrangement may operate all right notwithstanding a certain amount ofcontact bounce, but if the relay is required to operate at high speed,say thirty or more impulses per second, each impulse is oi relativelyshort duration and the portion of each impulse which may be lost due tocontact bounce becomes appreciable and may seriously interfere with theoperation of the circuit.

The invention provides a simple and effective means for eliminatingcontact bounce, comprising a resilient support for the make and breakcontact springs of a relay. According to the preferred embodiment of theinvention, the support consists of a body of soft rubber or equivalentresilient material which bears against the edges of the contact springsnear the contact ends thereof and is effective to prevent the springsfrom vibrating.

The invention will be described more in detail hereinafter, referencebeing made to the accompanying drawing, in which Fig. 1 is a top or planview of a relay embodying the invention;

Fig. 2 is a side view of the same; and

Fig. 3 is a partial section on the line 3-3, Fig. 1.

Referring to the drawing, the relay shown therein is for the most partor" known construction, and comprises a magnetic structure including anarmature, two working contact springs adapted to be operated by thearmature when the relay is energized, and make and break contact springswhich cooperate with the two working contact springs, respectively. Thisarrangement of contact springs provides for closing one circuit andopening another circuit upon energization of the relay. Various otherspring combinations may be employed.

The magnetic structure includes the core I 0, winding 6 l, and the heelpiece l2, the latter being attached to the core II) by means of amachine screw l3. The armature is indicated at H and has an integrallyformed arm i! for operating the working contact springs and twointegrally formed ears i6 and I1 by means of which it is pivotallysupported on the bracket it. This bracket is secured to the heel piecei2 by means of a washer I9 and screw 20 and has two integrally formedears 2| and 22 which extend between the ears i6 and ll of the armatureI4, as shown clearly in Fig. 1. The pivot rod 23 passes through holesdrilled in the ears it and ii and is rotatable in bearings formed in thecars 28 and 22.

The two working contact springs are indicated at 25 and 28. A breakcontact spring 28 cooperates with the working contact spring 25, whilethe make contact spring 21 cooperates with the working contact spring28. These contact springs are clamped to the heel piece E? by means of arectangular washer 33 and the two screws 3! and 32. The spring assemblyalso includes a plurality of insulators such as 36 and a stop 35 whichis located next to the heel piece.

The shape of the contact springs can be seen clearly in Fig. 1. Theworking contact springs such as 25 are relatively long and narrow,providing the necessary flexibility; while the make and break contactsprings such as 26 are shorter and wider, and generally speaking, arestifier than the working contact springs. The flexibility or stifinessof the springs is, of course, also dependent on the gauge of metal used,which varies with the operating characteristics required. The make andbreak contact springs such as 26 have side extensions at the ends whichproject into the path of the working contact springs such as 25. Theseextensions'carry contacts which cooperate with contacts on the workingcontact springs.

The working contact springs are tensioned downward, as the relay is seenin Fig. 2. Spring 28 bears against the bushing 30 on the arm 15 ofarmature i4, and arm it rests against the adjustable stop 35, by meansof which the normal position of the armature and spring 28 isdetermined. The stop 35 and make contact spring 27 are so adjusted thatthe working contact spring 28 is out of engagement with the make contactspring 27; that is, the contact is open. The working contact spring 25,on the other hand, is in engagement with .the break contact spring 26;that is, the contact is closed. The spring 25 carries a bushing 29,which lies between the springs 25 and 28. The adjustment should be suchthat this bushing is very nearly in engagement with spring 28, orperhaps in light contact therewith. It is preferable that spring 28 benormally slightly separated from bushing 29 so as to insure that thereis no reduction in contact pressure between springs 25 and 25,

The break contact spring 26 and the make contact spring 21 are supportednear their ends by an arrangement which will now be described. Thereference character 40 indicates a fiat rectangular bracket member'whichrests against the heel piece l2 and is secured thereto by a screw 4|. Atthe end opposite the screw 4| the bracket 40 is provided with a pin orstud 42 which may be secured to the bracket by riveting, as indicated inFig. 3. The stud 42 supports a cylindrical body of resilient insulatingmaterial indicated at 43, which may be a short section of rubber tubing.The tubing should have relatively thick walls and an internal diameterwhich i somewhat less than the diameter of the stud 42. The section 43is simply slipped onto the stud 42 where it is retained by its naturalelasticity.

Various resilient materials having good insulating properties may beemployed. A high grade pure gum rubber is very satisfactory. Syntheticmaterials such as neoprene may also be used, and are Preferable tonatural rubber in certain cases because of their greater resistance toattack by agents which cause the deterioration of natural rubber.

The contact springs of the relay may be ad- Justed before the bracket asand associated parts are assembled on the heel piece. then placed on theheel piece and the screw 4| is inserted, the position of the bracketbeing such that the resilient member 433 is well clear of the contactsprings. The screw ii should be turned in far enough to hold the bracketflat on the heel piece but not enough to prevent rotation thereof. Thebracket is then rotated on screw M to the position in which it appearsin Fig. 1, and the screw ti is tightened up so as to hold the bracketsecurely in this position.

As can be seen from Figs. 1 and 3,.when the bracket 48 is properlyassembled to the heel piece i2, as described in the foregoing, theresilient member 53 is brought into engagement with the edges of themake contact spring 26 and the break contact spring 2?, the springsbecoming indented in the resilient material. The material yields toaccommodate the springs and the overlapping material forms a resilientsupport both above and below each spring. If it should become necessaryto readjust the relay at any time, the screw 4!, is loosened up and thebracket 50 is rotated far enough in a clockwise direction so that theresilient member 13 is out of the way. After the adjustment is completedthe bracket 60 is moved back to operative position and the screw M istightened up again.

The adjustment of the bracket kill and resilient member 43 is notcritical. Care should be taken, however, to insure that the member 13 isactually in good contact with the springs so that the latter indent therubber, or other material of which the member :13 is composed, to asubstantial degree, as indicated in Fig. 3.

The winding H of the relay is provided with suitable terminals such asEd by means of which it may be connected in an electrical circuit. Thecontact springs also have integrally formed terminals such as 5! forconnecting them in the circuits which they are intended to control.

When the relay is energized the armature It is attracted by the core itand the arm l5 moves the working contact spring 28 upward. Spring 28immediately engages the bushing 29, whereupon the working contact spring25 is moved upward also. Thus the contact on spring 28 is brought intoengagement with the contact on make contact spring 21, while the contacton spring 25 is separated from the contact on the breakcontact spring26.

Considering the operation of the springs 28 and 21 somewhat more indetail, the distance traveled b the contact on spring 28 before itengages the contact on spring 21 is variable, but may be about .010inch, for example. This is the length of the-contact gap when the relayis deenergized. The distance traveled by the contact on spring 2! afterit is engaged by the contact on spring 28 is also variable, but shouldnot be so great that the spring 2! becomes permanently displacedrelative to the resilient member 43.

The bracket is The travel may be, for example, as much as .018 inchwithout any danger of permanent displacement. When the contact on spring21 moves upward, due to its engagement by the contact on spring 28, awarping action of spring 21 takes place, which reduces the distance thespring has to move upward at the point where its edge is engaged by theresilient member 43. This distance is small enough so that it is readilyaccommodated by the elasticity of the member 43 and no perceptibleslipping of the spring 21 relative to member 43 occurs. When the relayis deenergized, therefore, both springs resume the normal position towhich they have been adjusted.

As indicated hereinbefore, the armature I4 is sharply attracted upon theenergization of the relay which brings the contact on spring 28 suddenlyinto engagement with the contact on spring 21, striking it a blow whichin an ordinary relay would be apt to produce contact bounce. This effectis entirely eliminated in my improved relay, however, by the resilientmember 43 which engages the contact spring 21 and resiliently supportsthe same as described, entirely preventing vibration of the contactspring.

When the relay is deenergized, the contact springs resume the positionin which they are shown, spring 28 separating from spring 2! and spring25 coming into engagement with spring 26. The closing of this backcontact takes place suddenly, but there is no danger of contact bounce,due to the resilient support for spring 26 which prevents vibrationthereof.

The resilient member 43 is common to the contact spring 26 and 21 andcould support one or two additional contact springs as well. In the caseof a relay having an unusually large spring combination, the resilientmember may be made somewhat longer so as to take care of all the makeand break contact springs The arrangement described is completelyefi'ective, as has been demonstrated by numerous tests. Relays withvarious spring combinations showing contact bounce upon test have beenequipped with the invention and re-tested, with the result that nocontact bounce could be detected. As regards the life that. may beexpected, a relay provided with a resilient supporting member 43 madefrom a high grade of natural rubber has been energized and deenergized65,000,000 times without any appreciable change in the resilient memberor decrease in its effectiveness.

The invention having been described, that which is believed to be newand for which the protection of letters patent is desired will bepointed out in the appended claims.

I claim:

1. In a relay, 9. contact spring, a second contact spring adapted toengage said first contact spring to close an electrical circuit, and aresilient member pressing against the edge of said first contact springto prevent a momentary opening of said circuit by vibration of saidfirst spring when the same is engaged by said second spring.

2. In a relay, a working contact spring, a second contact spring adaptedto be engaged by said working contact spring. and a fixed body oiresilient insulating material in which the edge of said second contactspring is indented, whereby vibration of said second contact springresponsive to its engagement by said working contact spring isprevented.

3. In a relay, a working contact spring, a second contact sp g ad ptedto be engaged by said working contact spring, nd a body of resilientmaterial pressing against the edge of said second contact spring nearthe point where it is engaged by said working contact spring, said bodyhaving sufiicient elasticity to permit said second contact spring toyield when the same is engaged by said working contact spring.

4, In a relay, 9. working contact spring having a contact at the end, asecond contact spring having an offset portion bearing a contact adaptedto be engaged by the contact on said first spring, and a body ofresilient material pressing against the edge of said second springapproximately at 6. In a relay, a plurality of working contact springs,a plurality of interspersed contact springs cooperating with saidworking contact springs, respectively, said cooperating contact springshaving corresponding edge portions which are in alignment with eachother but are not in alignment with any edge portions of said workingcontact springs, and a body of resilient insulating material pressingagainst said aligned edge portions to prevent vibration of saidcooperating contact springs when the same are engaged by said workingcontact springs.

7. In a relay, a plurality of working contact springs, a plurality ofsprings cooperating with said working contact springs, respectively,said cooperating prings having sections which are out of alignment withthe corresponding sections of said working contact springs, a body ofsoft rubher, and means for supporting said body with one side thereofpressing against the said sections of said cooperating contact springsin a direction which is substantially at right angles to the directionof movement of said working contact springs.

8. In a relay, a working contact spring, a second spring cooperatingwith said first spring, a heel piece, means for supporting said springson said heel piece, a body of resilient insulating material, and meansfor adjustably supporting said body on said heel piece in two positionsin one of which the body presses against the edge of said second springto prevent contact bounce when the second spring is engaged by the firstspring and in the other of which the spring is disengaged by said bodyand is free for adjustment.

9. In a relay, a working contact spring. a second spring cooperatingwith said first spring, a heel piece, means for supporting said springson said heel piece, a body of resilient insulating material mounted onsaid heel piece so as to bear against the edge of said second spring toprevent contact bounce when the second spring is engaged by the firstspring, and means supporting said body on said heel piece adapted topermit the said body to be moved out of engagement with said spring tofacilitate adjustment thereof.

ARTHUR J. JOHNSTON.

